The editors and Göran Grimvall from Royal Institute of Technology (KTH) of Sweden explain why the just-published paper by Glensk et al. [Phys. Rev. X 4, 011018 (2014)] deserves broad dissemination and special recognition.

Gravity/fluid correspondence depicts the recent realization that the dynamics of the latter actually finds analogue in the former. Investigating this correspondence further, theorists now discover a counterpart of fluid turbulence in gravitationally perturbed black holes that gives rise to long-lived, large-scale ”gravitational wave tornadoes.”

Quantum spin Hall (QSH) insulators, with their insulating interior and conducting edges, have great potential for technological applications. But, scarcity and difficulty in fabrication are major obstacles to their wide applications. Theorists now predict that single sheets that can be exfoliated from two well-known layered thermoelectric compounds, ZrTe${}_5$ and HfTe${}_5$, are the most promising QSH insulator candidates to date.

The handedness of an object has always been a binary concept: either left handed or right handed. Scientists now show that quantifying handedness as direction-dependent properties actually makes fundamental physical sense and can guide both our understanding of known handedness phenomena and design of materials with novel handed-response properties.

Recent discovery of neuronal stimulation by low-intensity, focused ultrasound waves has ignited high hope and research effort to develop a noninvasive way to assess and control brain activity with millimeter spatial resolution. But how does the phenomenon work? Scientists now propose the first concrete biophysical model to explain, both qualitatively and quantitatively, the discovery and to guide the methodological development.

Optical activity—the ability to rotate the polarization of light—was long thought to be only the property of organic molecules without intrinsic structural mirror symmetry. Scientists now demonstrate experimentally that single carbon nanotubes, which have internal mirror symmetry, can be externally induced to exhibit both giant optical activity and a broad range of variability.

Topological insulators are classified by “topological invariants” characterizing their electronic structures. Identifying and computing topological invariants for insulators in which electron-electron interactions are important is, however, difficult. Theorists now present a way to accomplish this task for a wide range of topological insulators.

In magnetic materials known as spin ice, atomic-scale magnets on certain lattice structures can behave as if they were composed of independent “monopoles.” Scientists now demonstrate that those atomic-scale magnets in concert can fragment into both monopoles and a second fluctuating magnetic moment, with the monopoles forming a crystal and the second segments forming a disordered background magnetic liquid.

How does the geographic distribution of human populations correlate with their networks of social connections? In a simple mathematical model, theorists, for the first time, tie these two phenomena together and show that the model reproduces several interesting features found in real populations.

The Winfree model, a well-known mathematical model for describing collective synchronization in living systems, such as flashing fireflies, has been under-utilized because of its daunting technical complexity. Now scientists have found a way to dramatically reduce it to a technically tractable form and demonstrate the power of the reduction with findings of new “chimera” states in populations of pulse-coupled oscillators.

New two-dimensional materials artificially engineered to have unusual electronic properties will broaden the material basis for our quest for ever-smaller, more versatile electronic devices. Theoretical investigation of an artificial honeycomb lattice of zinc-blende semiconductor nanocrystals reveals a rich electronic structure that is part graphene-like and part topological-insulator-like, indicating a new direction of electronic-materials engineering.

Device-independent quantum cryptography protocols exploit quantum correlations generated by “black box” quantum devices. The physical dimensionality of such devices may act as a constraint. But which quantum correlations are fundamentally attainable and can be exploited under this constraint? Scientists now develop a new and timely numerical method that answers this question.

Realization of quantum computing requires not only qubits that are robust against noise but also control over the crosstalk (entanglement) between them. Following the very recent experimental realization of quantum-dot-based “exchange” qubits, theorists propose a practically feasible method for entangling two such qubits in a controllable way.

By putting electrons through a phase-modulation hologram, a thin film of silicon nitride with nanoscale grooves of different thicknesses, scientists achieve, for the first time, the generation of diffraction-free electron Bessel beams.

Both the integer and the fractional quantum Hall effects of a two-dimensional electron gas involve one-dimensional channels of electronic transport along edges of the sample. Experimentalists now reveal the internal structures of these edge channels in unprecedented microscopic detail.

In optomechanics it is known that driving a micromechanical oscillator with a laser field can lead to generation of “nonclassical” quantum states of the oscillator. Researchers now fill a theoretical gap by offering an analytical theory to describe the laser-oscillator interaction in a regime of interesting oscillator quantum mechanics and predict “nonclassical” oscillator states where they were unexpected.

Quantum data locking (QDL), proposed as a conceptually different alternative to quantum key distribution, uses a small secret key to lock a much longer message for secure transmission. For practical use, QDL must be robust against noise. Theorists lay the necessary theoretical ground for development of QDL protocols using noisy quantum channels.

Quantum effects may help devise new imaging schemes that can overcome classical constraints posed by noise and diffraction. By using squeezed states of light in photonic force microscopy (PFM), scientists have demonstrated a 14% quantum enhancement of PFM’s spatial resolution, imaging details of living yeast cells with a resolution of 10 nm.

Point defects can significantly alter the behavior of solid-state materials, but a theoretically and experimentally consistent understanding of their formation energy has been lacking so far. Taking into account anharmonic lattice vibrations, a new state-of-the-art theoretical effort makes a very significant advance toward filling that gap and demonstrates a critical need to revise the official international point-defect database.

Experimentally determining the lattice thermal conductivity of materials with very high or low values is expensive and time consuming. An efficient computational approach using machine-learning techniques finds a much larger range of conductivity than expected for an impressive number of half-Heusler compounds and also offers a way to rapidly evaluate other classes of materials.

Classical theory used to define the rate constant of a chemical process drastically overestimates the rate of many single-molecule processes, and derived theories designed to compensate for overcounting only work well in limited situations. A new ”spectral rate theory,” addresses these issues and its effectiveness is demonstrated on both numerically generated and experimental data.

Friedel oscillation refers to the quantum interference phenomena where electrons in a solid form standing waves on the solid’s surface as a result of scattering by defects. A combined theoretical and experimental work shows that Friedel oscillation can open an energy gap in graphene.

The classical Green-Kubo formula, capturing the essential physics of particle diffusion, is one of the most fundamental important results in statistical physics, but has recently been found to be invalid for systems that never reach equilibrium. A generalization of the formula to such “aging” systems is provided here, laying down a new fundamental piece of contemporary statistical physics.

Large-scale ordering of nonelementary mesoscopic magnetic structures is both fundamentally fascinating and technologically relevant. A theoretical study of frustrated quantum magnets predicts the emergence of a new class of stable magnetic vortex crystals under general conditions.

The maximum packing density of particles is greatly affected by their shape, an important issue in nanotechnology, biology, and industry that is nevertheless poorly understood mathematically. This comprehensive study takes an analytical and computational approach to calculating the highest-known packing density of over 55,000 related shapes, leading to new guidelines on how to prepare particles for maximum packing efficiency.

Tensor networks are used to represent the wave functions of quantum many-body systems, but the standard approaches only consider two-body entanglement and do not work well for “frustrated” systems, where the underlying lattice geometry makes three- or many-body entanglement also important. A new tensor-network approach based on a novel tensor concept for describing such “simplex” entanglement shows great promise.

Secure encryption is essential in today’s world, and to beat illicit decryption, evermore secure schemes are needed. Inspired by cardiorespiratory coupling, a new scheme, radically different in concept from the existing encryption approaches, uses the coupling functions between two dynamical systems such as electronic oscillators to enable secure communications.

Laser filaments are a promising means of transporting light energy over long distances, but they can only carry an average power of a few watts, thus limiting certain applications. Experiments now overcome this limitation by demonstrating that the thermal wake of a bundle of filaments provides a long-lived air waveguide that can channel laser beams with an extremely high average power.

A normal renewal process is a sequence of independent events with the between-event time following the Poisson distribution. More complex renewal processes can “age,” characterized by non-Poissonian waiting-time distributions. A new theoretical approach dissects such aging renewal processes and offers many new insights, including how measurements on these processes should be unambiguously interpreted.

The Casimir force operating between two objects placed in a vacuum has its origin in the “virtual photons” that fill the vacuum. A combined experimental and theoretical investigation establishes a complete landscape for this force between a single atom and a metal grating—a problem not only of fundamental interest but also relevant to surface quantum optical experiments.

Oxides containing both carbon and silicon had been elusive. One such oxide was synthesized under high pressure in 2011, but its structure was not known. An extensive computational search enabled by an evolutionary algorithm finds SiC${}_2$O${}_6$ to have a crystalline structure that is stable under pressure as high as two hundred times the ambient pressure.

“Weak-value amplification,” an interference effect that was introduced quantum mechanically, but can also be realized using classical electromagnetic waves, uses only a small fraction of the available events to make precise measurements. How can this be? Theorists reveal that weak-value amplification achieves that by funneling all the information into a small fraction of events.

“Weak-value amplification,” a quantum-mechanical phenomenon discovered only two decades ago, has received considerable interest for its potential as a metrological tool. However, its operation requires special circumstances, therefore carries costs. A new analysis shows that the associated costs outweigh the advantages when compared to other methods of signal amplification.

How does a superconductor in contact with another through an atomic-scale junction influence the electronic properties in the latter? Investigating a submicron superconducting island of single-crystal Pb embedded in a pre-superconducting Pb crystalline monolayer, scientists reveal a giant region of induced superconductivity in the monolayer and also offer a theory for describing such proximity effects.

Quantum dots in a monolayer transition metal dichalcogenide such as MoS${}_2$ hold the promises of low dimensionality and dual electrical and optical functionality. Scientists provide the first and necessary theoretical framework for studying such quantum dots, laying the basis for further theoretical and experimental investigations.

Multiferroics, complex materials with exotic collective ordering of their intrinsic microscopic magnetic and electric dipoles, are highly sought after. BaFe${}_{12}$O${}_{19}$ is now predicted to be the first multiferroic material hosting both ferrimagnetism and antiferroelectricity—an ideal candidate for realizing room-temperature multiple-state memory devices.

Topological quantum computing avoids the problem of decoherence by using noise-resistant non-Abelian anyons to carry quantum information. Materials hosting these exotic particles are scarce, however. Scientists now show that Fibonacci anyons—the holy grail for topological quantum computing—can be realized in a heterostructure composed of a simple fractional quantum Hall material and a conventional superconductor.

Pure LaMnO${}_3$ is an antiferromagnetic insulator but when doped with additional charge carriers, it can become a ferromagnetic conductor, with a seemingly ferromagnetic insulating phase intervening in between. An experimental investigation reveals that the intervening phase is a new state that may be characterized as a “superspin glass.”

Wave packets of light have been made to travel in a curved space along geodesic paths, generating optical analogues of general-relativity phenomena. A new analysis of the curved-space generalization of the Maxwell equations shows that wave packets can also travel along nongeodesic paths while changing and recovering their shapes periodically.

Topologically nontrivial surface current is the hallmark of a topological insulator (TI). Its unambiguous identification is, however, plagued by presence of trivial current channels. Using simultaneous local and nonlocal transport measurements, scientists make high-precision identification of genuine TI-related surface current.

Magnetite, discovered in ancient Greece, transitions from a simple cubic lattice to a monoclinic one with much greater resistivity when cooled to 124 K. The fundamental nature of the transition has remained a puzzle. A new experimental study shows that, despite their apparent differences in structure and electronic transport, the two phases across the transition are linked by a persistent presence of electronic correlations.

Information, ideas, or diseases spread through interactions between individuals. The temporal pattern of such interactions is known to show “burstiness,” but little is known about how it affects large-scale spreading dynamics. Analytic results on a simple model of bursty spreading dynamics provide a rare, but much needed reference point for numerical simulations and empirical data analysis.

How to describe the “electric double layer” that is at the root of all electrokinetic phenomena such as electrophoresis and electro-osmosis? A new theoretical approach, introducing the concept of a surface potential trap and applying the constraint of global charge neutrality rigorously, answers this century-old question in the context of contemporary electrokinetics involving nanoscale systems and time-dependent electric fields.

Atomically thin semiconductors, e.g., MoS${}_2$, may be an alternative to silicon in transistor electronics, but their electron mobilities as measured are apparently rather low. A theoretical study shows that the low mobilities are caused by the scattering of electrons by charged impurities and points to high-$\kappa$ dielectric coatings as a way to boost the mobilities of high-impurity samples.

Atoms, organic molecules, and polymerized DNA can all form polygon networks, despite enormous differences in their sizes and interactions. Scientists find the geometry, and strength of interactions, of building blocks to be the unifying factors for network assembly and codify them in the concept of an effective, material-dependent “patchy particle.”

A system of loosely packed little solid balls is an intriguing sonic material in which sound travels always as shock waves. A new theoretical investigation reveals a number of interesting findings about the inner workings of such shock waves, including the emergence of a fluidlike state in the wake of a shock wave.

Do photoelectrons, excited, and then liberated from a solid, by ultraviolet or x-ray light, change their spin orientations? Earlier work reported that they always did if the light used was circularly polarized. A new combined experimental and theoretical study reveals that the answer actually depends on the full symmetry properties of the states the photoelectrons are first excited to.

Social, technological, and biological networks are known to organize into modules or “communities.” Characterizing and identifying modules is highly nontrivial and still an outstanding problem in networks research. A new approach uses both the concept of modular hierarchy for network construction and the methods of statistical inference to address this problem, succeeding where the existing approaches see difficulties.

“Ballistic spin resonance” refers to the counterintuitive phenomenon in which spin-polarized electrons moving down a conducting wire lose their collective spin polarization at special values of an applied magnetic field. A quantum-mechanical treatment shows that electron spin-orbit coupling and quantum confinement are at the root of the phenomenon.

Ultrasensitive optical sensing based on surface plasmons requires nonintrusive weak light and a large signal-to-noise ratio. Using quantum mechanically entangled photon pairs, experimentalists exploit the quantum entanglement for noise cancellation and achieve sensing at the single-photon scale and in the presence of a noise level 70 times higher than the signal.

Quantum processing tomography typically reconstructs an unknown quantum dynamical operation by measuring its effects on known states of a quantum device. Taking a different approach of comparing the operation of interest to a set of finite and easily implementable reference operations, a new method can reconstruct any quantum operation reliably.

Topological quantum computation using non-Abelian anyons—exotic particlelike excitations that are neither bosons nor fermions—as qubits has been thought to be in no need of error correction. Theorists now show that active error correction is in fact necessary and offer a method for performing it.

Conventional phase transitions are usually characterized by a change in a fundamental thermodynamic observable, e.g., in density when liquid changes to vapor. A theoretical study of a one-dimensional disordered quantum spin chain reveals a new class of quantum phase transitions that leave no such signatures and pins down their origin.

Each dendrite in a biological neuron has long been thought to process the multiple inputs it receives in a simple additive fashion. Recent experiments, however, have demonstrated occurrences of nonadditive dendritic input processing. Theorists find that such single-neuron nonlinearity makes memory retrieval in a network of neurons more resilient to noise.

The celebrated Fermi-Pasta-Ulam recurrence phenomenon in nonlinear dynamics was first demonstrated experimentally in optical fibers 50 years after its theoretical discovery. But it was expected to be suppressed when the so-called third-third-order dispersion (TOD) became relevant. A new optical-fiber experiment shows that it not only survives in the presence of TOD, but disappears and reappears several times as the optical pump frequency is varied.

In the quest to understand atomic nuclei, laser spectroscopy is a valuable tool. Combining laser excitation and ionization of atoms with tracking and analysis of the associated alpha decay, a novel technique demonstrates its capability to probe with high sensitivity the hyperfine structure of exotic nuclear isotopes and determine their fundamental nuclear observables.

A new ultrafast optical spectroscopy experiment establishes, for both cuprates and pnictides, a remarkable systematic, nonmonotonic variation of their highest superconducting critical temperature with the strength of the electron-phonon interaction in them.

Use of nitrogen-vacancy (NV) centers in diamond for quantum applications requires fast switching between their two different charge states. Using a diamond diode, scientists now demonstrate for the first time deterministic, purely electrical, and room-temperature charge-state control of single NV centers on the time scale of a microsecond.